Various packaging techniques have been used to build a load of unit products and subsequently wrap them for transportation, storage, containment and stabilization, protection and waterproofing. One system uses wrapping machines to stretch, dispense, and wrap packaging material around a load. The packaging material may be pre-stretched before it is applied to the load. Wrapping can be performed as an inline, automated packaging technique that dispenses and wraps packaging material in a stretch condition around a load on a pallet to cover and contain the load. Stretch wrapping, whether accomplished by a turntable, rotating arm, vertical rotating ring, or horizontal rotating ring, typically covers the four vertical sides of the load with a stretchable packaging material such as polyethylene packaging material. In each of these arrangements, relative rotation is provided between the load and the packaging material dispenser to wrap packaging material about the sides of the load.
In many commercial applications, typical loads wrapped by a stretch wrapping machine have a substantially cuboid shape with a relatively consistent length, width and height throughout, and in many cases having a similar length and width to the supporting pallet. Generally, in these applications, loads consist of multiple layers of the same products. In other applications, however, loads may deviate from this traditional configuration, and may include portions or layers, herein referred to as inboard portions, that are substantially inboard of a supporting body upon which they are disposed and to which they must be secured. For example, loads that are palletized using an automated pallet picker may end up with less than complete layers of products on the top layer, and as such the top layer may therefore be substantially inboard from the corners of the main body of the load. In some instances, only one product, or one case of products, may be placed on the top layer of the load. As another example, some loads may have a “ragged” topography due to the inclusion of multiple products or cases of products having varying elevations at different points across the top of the load. As another example, some products loaded onto pallets may be substantially smaller in cross-section than a pallet, and may therefore be substantially inboard from the corners of the pallet.
It has been found that stretch wrapping machines that are optimized to handle typical, cuboid-shaped loads may have difficulty in securing inboard portions of loads, loads with ragged topographies in an automatic cycle, and other instances including nonstandard top layers. Many stretch wrapping machines, for example, wrap in a spiral fashion, and include an elevator system that moves an exit point of a packaging material dispenser generally parallel to the axis of relative rotation between the load and the packaging material dispenser during the relative rotation. For portions of a load that are significantly inboard, this movement parallel to the axis of relative rotation may leave flaps of packaging material that cannot reach and secure the inboard portion of the load to the pallet or to the main body of the load. Even if the exit point is moved to a point at which the packaging material clears the pallet or main body of the load and wraps the inboard portion, the inboard portion is typically secured inadequately, and in many instances, a risk exists that the packaging material will break as the edge of the material snags on the corner of the pallet or the main body of the load. Further, the ragged top surfaces of some loads may present numerous sharp points and corners that could potentially tear or puncture the packaging material.
In still other applications, it may be desirable to secure top sheets of packaging material or cardboard onto loads, e.g., to protect the top of a load from dust, moisture or damage from another load stacked on top of the load, or to secure slip sheets onto loads to support other loads that may be stacked on top of the loads. Effectively securing a top sheet or slip sheet remains problematic in some situations, particularly for loads of easily-deformable articles such as paper products and plastic bottles, since damage to articles located at the top corners of such loads may occur as a result of excessive wrap force applied to the top corners.
Therefore, a significant need continues to exist in the art for an improved manner of reliably and efficiently loads with nonstandard top layers.